Cooling duct piston for a direct-injection diesel engine

ABSTRACT

The aim of the invention is to obtain, with constant or increasing output, a reduction in the compression height of a cooling duct piston ( 1 ) for a direct-injection diesel engine. To this end, the piston ( 1 ) is composed of at least two parts ( 23 ) that are soldered together. One of the parts is a piston base body ( 2 ), which is forged of steel and which is provided with a shaft ( 8 ), hubs ( 6 ) and with an annular part ( 9 ). The other part, which is made of steel or of a nickel-based material, contains a combustion recess ( 4 ) and at least a portion of the piston head ( 5 ). The piston base body ( 2 ) and the second part ( 3 ), together, form a cooling duct ( 11 ) that can be filled with oil.

[0001] The invention relates to a cooling channel piston for a diesel engine with direct injection.

[0002] Up to the present time, such pistons have mostly been structured as cast aluminum pistons or as so-called pendulum shaft pistons, and have been used as standard items by many motor vehicle manufacturers.

[0003] The invention deals with the problem of finding a piston concept that allows a reduction in the compression height of the piston, while keeping the engine output the same, or increasing it.

[0004] This problem is solved, in the case of a piston of the type according to the preamble, by means of a structure having the features indicated in claim 1. Advantageous further developments are the object of the dependent claims. The compression height of pistons according to the invention lies in the range of 0.35 to 0.6× piston diameter, and preferably at approximately 0.4 to 0.45× piston diameter (D).

[0005] The second part, which contains the combustion trough, can be structured as a machined forged part.

[0006] The invention will be explained in greater detail below, using an exemplary embodiment. The drawing shows:

[0007]FIG. 1 a piston according to the invention in cross-section, cut in the pin direction,

[0008]FIG. 2 a piston according to the invention in cross-section, cut in the pressure/counter-pressure direction.

[0009] The piston 1 consists of a base body 2 and a component 3 that is soldered to the former, which component comprises a combustion trough 4 and a part of the piston head 5. The base body comprises the hubs 6 with the hub bores 7, the shaft 8, the ring part 9, and the ridges 10, which form part of the inside shape of the piston on the pressure side and the counter-pressure side. The ridges 10 run at the same or approximately the same axial height, radially towards the inside, and form a contact surface for the component 3 in the pressure/counter-pressure direction. The combustion trough 4 lies circumferentially on machined surfaces of the ridges 10 with its lower region, and makes contact in the region of the hubs or hub support, whereby the machined surfaces of the ridges and the hub support lie in a single plane, and a turned groove with a height difference 14 is formed in the ridges as a result of the machining.

[0010] In other embodiments according to the invention, the combustion trough can also rest on the hub support and the ridges 10 only locally, instead of circumferentially.

[0011] The shaft of the piston is recessed in the pin direction and forms a box shape. The base body 2, and the component 3 soldered to it, together form a cooling channel 11 that can be filled with motor oil.

[0012] The base body 2 consists of forged AFP steel. The component 3 also consists of steel, but can also consist of a nickel-based material that is resistant to high temperatures.

[0013] The base body 2 and the component 3 are connected with one another by means of a radial solder seam 12 and an axial solder seam 13.

[0014] The central part of the combustion trough 4 forms part of the interior shape of the piston, with its surfaces that face downward.

[0015] The compression height of the piston is 0.43×D. 

1. Cooling channel piston (1) for a diesel engine with direct injection, having the characteristics: the piston (1) consists of at least two parts (2, 3) soldered to one another, one of which is a piston base body (2) forged from steel, having a shaft (8), hubs (6), and a ring part (9), and the second part (3) of which, consisting of steel or a nickel-based material, comprises a combustion trough (4) and at least a part of the piston head (5), and whereby the piston base body (2) and the second part (3) together form a cooling channel (11) that can be filled with oil, the second part (3) is seated on the base body (2) above the hubs (6) in the pin direction, with the lower region of the combustion trough (4), and on the ridges (10) of the base body that run from the shaft (8) or from the ring part (9) radially towards the inside, in the pressure/counter-pressure direction, whereby the contact surfaces in the pressure/counter-pressure direction and in the pin direction lie in the same mechanically machined plane, and the base body (2) and the combustion trough (4) are soldered to one another in this plane, and whereby at least the surface or surfaces of the ridges (10) that face the piston head run at an axial height that remains the same or approximately the same, if applicable aside from the height difference (14) that is formed by a turned groove that holds the lowest region of the combustion trough (4), and aside from rounding radii in the transition from the ridge (10) to the shaft (8) or to the ring part (9), respectively, the central region of the combustion trough forms a part of the inside shape of the piston with its surface that faces downward and its surface that faces radially inward, the compression height KH lies in the range of 0.35 to 0.6×D, whereby the height KH represents the axial distance between the center axis of the hub bores and the upper edge of the piston head, the base body (2) and the second component (3) are connected with one another by means of a solder seam (13) that runs axially, in the region of the piston head, or by means of a radial seam that lies in the region of the top land.
 2. Cooling channel piston according to claim 1, characterized in that the piston base body consists of AFP steel.
 3. Cooling channel piston according to one of the preceding claims, characterized in that the shaft walls of the piston that contain the hubs are recessed to a width of <0.8× piston diameter in the pin direction.
 4. Cooling channel piston according to one of the preceding claims, characterized in that the top edge of a rod connected with the piston lies at the level of the lower region of the combustion trough. 